1. Field of the Invention
The present invention generally relates to broadband communication systems. In particular, the present invention relates to broadband communication systems that use the Data Over Cable Service Interface Specification (DOCSIS) media access protocol or any derivatives, including but not limited to a DOCSIS-compliant two-way satellite communications system.
2. Background
DOCSIS (Data Over Cable Service Interface Specification) generally refers to a group of specifications published by CableLabs that define industry standards for cable headend and cable modem equipment. In particular, DOCSIS specifies modulation schemes and the protocol for exchanging bidirectional signals over cable. Recently, however, the use of the DOCSIS protocol has expanded beyond the cable industry. For example, modified DOCSIS technology is in development by both satellite and wireless providers for two-way access into subscriber homes. Furthermore, DSL suppliers are adopting DOCSIS-like processes to help them finally converge on an interoperable standard.
Common to all DOCSIS-based broadband data communication architectures is the transfer of data between a central location and many remote subscribers over a shared communications medium. The terms used to describe the central location vary depending on the type of communication architecture: for example, in cable systems, the central location is typically referred to as the headend, in broadband terrestrial fixed wireless systems, it is typically referred to as a wireless access termination system (WATS), and in two-way satellite communication systems, it is typically referred to as the satellite gateway. Terms used to describe subscriber equipment also vary depending on the type of communication architecture: for example, in cable systems, such equipment is typically referred to as a cable modem (CM), in broadband terrestrial fixed wireless systems, it is typically referred to as a wireless modem (WM), and in two-way satellite communication systems, it is typically referred to as a satellite modem (SM).
For the purposes of the description provided herein, terminology pertaining to two-way satellite communication systems will be used. However, as will be discussed in more detail below, the present invention is not limited to two-way satellite communication systems, and may be used, for example, in any DOCSIS-based broadband communication system.
FIG. 1 illustrates the basic elements of a two-way satellite communication system 100. System 100 includes a satellite gateway 102 with associated antenna and transceiver 104, a satellite 106, and a satellite modem 108 with associated antenna and transceiver 110. As will be appreciated by persons skilled in the relevant art(s), satellite 106 facilitates bidirectional communication between satellite gateway 102 and satellite modem 108. The communication path from satellite gateway 102 to satellite modem 108 is typically referred to as the downstream while the communication path from satellite modem 108 back to satellite gateway 102 is typically referred to as the upstream.
In accordance with DOCSIS, satellite gateway 102 sends media access control (MAC) management messages to satellite modem 108 for a variety of purposes. One of these messages is called an Upstream Channel Descriptor (UCD) message. The purpose of the UCD message is to describe the attributes of a given upstream channel in sufficient detail so as to enable satellite modem 108 to successfully communicate with satellite gateway 102.
It has been observed, however, that additional upstream parameters beyond those defined in the DOCSIS UCD message are required in order to adequately describe a channel for satellite applications. Additionally, it would be desirable to provide additional upstream channel parameters not included in the DOCSIS UCD message to enable more efficient communication between a satellite gateway and satellite modems. Unfortunately, DOCSIS does not provide a vehicle for communicating these additional upstream parameters.
What is needed then, is a mechanism for communicating parameters pertaining to an upstream channel between a central location and subscriber equipment within a DOCSIS-based system, such as a DOCSIS-based two-way satellite communicate system, wherein such parameters are not included in a standard DOCSIS UCD message. Furthermore, the desired mechanism should permit backward-compatibility with conventional DOCSIS-based equipment.